The present invention relates to a semicondutor device; and, more particularly, to a method for forming a lower electrode for use in a semiconductor device by using an electroplating method.
As is well known, a dynamic random access memory (DRAM) with at least one memory cell comprised of a transistor and a capacitor has a higher degree of integration mainly by down-sizing through micronization. However, there is still a demand for down-sizing the area of the memory cell.
To meet the demand, there have been proposed several structures for the capacitor, such as a trench type or a stack type capacitor, which are arranged three-dimensionally in a memory device to reduce the cell area available to the capacitor. However, the process of manufacturing three-dimensionally arranged capacitor is a long and tedious one and consequently involves high manufacturing cost. Therefore, there is a strong demand for a new memory device that can reduce the cell area with securing a requisite volume of information without requiring complex manufacturing steps.
Since capacitance is a function of dielectric area and the dielectric constant of the dielectric material, there have been introduced a high K dielectric, e.g., barium strontium titanate (BST) or the like, as a capacitor thin film in place of conventional silicon oxide film or silicon nitride film to increase capacitance in a given area. However, the use of high dielectric constant materials presents a problem when using a conventional material like ruthenium (Ru) as an electrode. The Ru electrode creates leakage current in the capacitance device.
Therefore, platinum (Pr) is suitable for use as electrodes in this situation. However, Pt is very difficult to be patterned by a conventional process such as a reactive ion etching (RIE), vertically, which, in turn, gives sloped sidewalls to a patterned thick Pt layer.
Thus, there remains a need for a method of forming an electrode compatible with a high K capacitor dielectric without representing the above-described problems.
It is, therefore, an object of the present invention to provide a semiconductor device incorporating therein lower electrodes which are formed by using an electroplating method.
In accordance with one aspect of the present invention, there is provided a method for manufacturing a semiconductor device for use in a memory cell, the method comprising the steps of: a) preparing an active matrix provided with at least one transistor, a plurality of conductive plugs electrically connected to the transistors and an insulating layer formed around the conductive plugs; b) forming a seed layer on top of the active matrix; c) forming a dummy oxide layer on top of the seed layer; d) patterning the dummy oxide layer into a predetermined configuration, thereby exposing portions of the seed layer which are located on top of the conductive plugs; e) filling the exposed portions with a first conductive material to a predetermined thickness; f) removing the dummy oxide layer; g) removing portions of the seed layer which are not covered with the conductive material, thereby obtaining lower electrodes; h) forming a capacitor dielectric layer on the lower electrodes; and i) forming a second conductive layer on the capacitor dielectric layer.